This invention relates to a process for anodically oxidizing aluminum and to products produced by such process. The term aluminum is used herein to include aluminum base alloys which, like pure aluminum can be electrolytically anodized to form oxide coatings or layers. More particularly, this invention relates to an improved process for anodically oxidizing continuous webs of relatively thin aluminum foil to produce a laminated anodized aluminum article which can readily replace articles presently made from aluminum sheet which is anodized on both side, for example base plates for lithographic printing plates.
Aluminum and aluminum base alloys in sheet and strip form have been continuously anodized by a number of techniques for many years. Such anodized products are used for electrical and decorative purposes, in the manufacture of household appliances, automotive trim, building materials, farm equipment, furniture, sporting goods, cans, container closures, lithographic plates, transformers, and in many other market and product areas.
A commonly employed technique for introducing anodizing direct current into a moving aluminum web is the use of a cathodic contact cell.
The so-called energy crisis has created a need to conserve energy sources by reducing the consumption of energy and/or by increasing productivity without increasing the amount of energy required. The anodizing of aluminum is an electrochemical process requiring substantial amounts of electrical energy and the present invention makes it possible to reduce by as much as one-half the amount of current required to anodize aluminum or, stated differently, the present invention makes it possible to anodize up to twice as much aluminum without increasing the electrical energy needed to conventionally anodize aluminum continuously using a contact cell arrangement.